Method of detonating explosion type rivets



Oct. 28, 1952 s. 'r. SPECIAL METHOD OF DETONATING EXPLOSION TYPE RIVETS Filed June 13, 1949 I=I 'E l A l2 m km I I v we [I 7 c v l? Z- 3nnentor C(ttorneg Patented Oct. 28, 1952 UNITED STATES PATENT OFFICE METHOD OF DE-TONATING EXPLOSION TYPE RIVETS Salvatore T'. Special, Fort Worth, Tex., assignor to Consolidated Vultee Aircraft Corporation, San Diego, Calif., acorporation of Delaware Application June 13, 1949, SerialNo. 101,122

2 Claims.

character, a typical example is given in U. S.

Patent #2,080,220Bitter, issued'May 11,1937.

Explosive rivets, which are alike in general appearance to solid rivets and are made in a similar variety of diameters, lengths, and head shapes, are usually employed for the fastening together of structural elements Where the areas adjacent the shank end of the rivet are inaccessible or in a blind location. 'The rivet is inserted into suitably aligned holes through the materials to be fastened and heat is applied to the pre-formed head end of the rivet. The heat is conducted through the rivet to the explosive charge in the shank portion, causing detonation of the charge and expanding the material of the shank end into a bulbularshape. 'This imparts a tension-resisting deformation or head to the rivet, completing its installation.

The present invention relates to an improvement in the method of heating the rivet to cause its explosionyand is applicable to any type of explosive rivet designed'to be'detonated by heat. Heretofore, specially designed and constructed rivet heating devices have been employed for the detonation of explosive rivets consisting essentially of a soft iron core provided with'an electrical coil mounted upon one end thereof and adapted upon energization to heat thecore, one end of which is placed against'the pre-formed head of the explosive rivet when in position in the work, the heat'irom'the core bein conducted through the rivet body to explode the charge. The heat required to explode rivets of this type, is of such a nature that considerable electrical energy is necessary in order to heat theiron core of such an apparatusand thec'oil required is of such size that the tool is bulky and. awkward to handle. 'Riveting of the general type contemplated by the present invention is usually carried out on-structures of a rather complex nature, as for example, in aircraft manufacture, wherein the space adjacent the formed head of the rivet is restricted by surrounding structure and where access 'to the rivet on installation is 'difilcul-t. The necessity for the use of a cumbersome tool in such work is a distinct disadvantage and results in increased labor costs and defective work. A further disadvantage in the use of electrically heated irons of the type thus described, resides in their requirement for a high degree of adjustment and the excessive maintenance of the iron tip. Considerable pressure is necessary in applying this type of rivet heating iron, and a relatively high degree of workmanship is necessitated in order to center the iron on the rivet head without contacting the metal portions adjacent to the rivet and in preventing the iron from occasionally slipping from the rivet head resulting in burning of the surrounding metal. Still a further disadvantage of electrically heated equipment of this type resides in its relatively high initial cost. One of the principal objects of the present invention lies in its simplicity and consequent nominal cost.

The present invention comprises the method of detonating explosive rivets of the type under consideration by heat created in the rivet head by frictional means. It is contemplated that this improved method maybe accomplished by contacting the pre-formed head of the positioned rivet with a specially designed rotating tool to create a sudden and localized rise in temperature to explode the rivet charge. The principal object of the invention is therefore, to provide an improved method of detonating explosive rivets by frictional means consisting of a simple and inexpensive rotatable tool.

These and other objects and the various advantages of the present invention will be apparent from the following description and the drawings which form a part of this specification, in which like numerals of reference denote similar parts throughout the several views.

In the drawings;

Fig. 1 is a partial section of a rotary tool as contemplated by' this invention'for detonating explosive rivets by frictional means.

Fig. 2 is a view illustrating the methodof detonatingexplosive rivets contemplated by the present invention, in which the use of a conventional'drill motor is employed.

Fig. 3 is an illustration of the contemplated method for exploding rivets in which a conventional angle-drill attachment isshown' to indicate the advantages residing in the use of the improved method in congested or confined work areas.

- The device illustrated in connection withthe improved method of the present invention constitutes a preferred embodiment, but it will be apparent from the following description that the objectives of the present invention may be ob tained by means of a wide variety of similar devices without departing from the nature and principles of the invention. a

The invention comprises an improved method and means for fastening two or more structural members as illustrated by the sheets A and B of Fig. 2, together by means of explosive type rivets C. The upper rivet C in Fig. 2 represents a conventional explosive type rivet inserted through suitable aligned holes I and 2 in the work pieces A and B respectively, in an unexploded condition. Rivets of this general type comprise a pro-formed head 3, an elongated cylindrical shank portion 4, an axial recess or bore extending into the shank end of the rivet, and an explosive charge 6 located within the recess 5. Conventionally, the charge 6 is of such a nature that it detonates'at elevated temperature. Upon detonation, the exposed portion of the shank 4 projectin beyond the work pieces A and B is swelled as indicated in the lower portion of Figure 2 to form a bulbular head I securely fastening the work pieces A and B together.

In distinction to the conventional method of raising the temperature of the rivet C sufiiciently to cause detonation of the charge 6 by means of contacting the rivet head 3 with an electrically heated iron, the present invention is characterized by the method of elevating the temperature of the rivet head 3 by frictional means; the heat thus created being conducted to the charge 6 to cause detonation. In the present embodiment,

' this is accomplished by the use of a novel form of rotary tool I0.

As illustrated in Fig. 1, the tool It) comprises a tip portion II and a projecting shaft portion l2 axially aligned and fastened together by means of threads I3 provided on one end of the shaft I2 to engage a threaded bore I4 in the tip II.

The shaft I2 may be secured to the tip portion II by any means such as a, drive fit, splines, or

a pin. Since the tool is adapted for rotation at high speeds, it is precisely balanced to insure accurate control.

The tip Ill may be formed of a variety of materials having relatively high coefficients of friction and low abrasive characteristics, and we have found that ordinary phenolic resin is particularly suitable for the intended purpose. Micarta, hard rubber, wood or any material having similar properties including relatively high coefficients of friction without excessive abrasive characteristics will also produce satisfactory results. The end face I5 of the tip II is provided with means for contacting a substantial area of the rivet head 3, such as a concave depression I6 generally conforming to the curvature of the formed rivet head 3 when the tool is to be used for exploding rivets of the oval or brazier head type. Obviously, the face I5 of the tip II may be similarly shaped to accommodate other rivet head shapes, in such a manner that the end face I5 is adapted to contact a substantial area of the head of the rivet when brought in contact therewith.

In employing the improved method of the present invention as illustrated in Fig. 2, the shank portion I2 of the tool I0 is inserted in and rapid- 1y clamped within a collet type chuck ll of an electric or air-driven type hand drill motor I8. Power to energize the motor I8 is conducted to it by means of a, conduit I9 and is controlled by a trigger switch incorporated in a handle portion 2| forming a part of the housing of the motor I8.

In utilizing the improved method contemplated by the present invention, the motor I8 is energized by operation of the trigger switch 20 to rotate the tool ID at a high rate of speed. While rotating, the pre-formed head 3 of the rivet C is contacted with the end face I5 of the rotating tool I0. Friction between the material of the rivet and the tool I0 builds up a sudden and intense elevated temperature within the rivet C causing detonation of the charge 6 and consequent deformation of the shank 5 to form the bulbular head I. I have found that by using phenolic resin as material for the tip portion II, a desirable quick rise in temperature is obtained within the rivet C without burnishing or other deleterious effects on the head 3 thereof. Since the temperature rise Within the rivet is principally dependent upon the relative speed between the stationary rivet head 3 and the rotating tip I I, it is advisable to apply only a moderate amount of pressure on the rivet head, rather than pressing the tool against the rivet head to the point where the speed of the motor is decreased. Since pressure of the tool against the rivet head is not important in performing the contemplated method, damage to the surrounding material by reason of inadvertent slippage of the imity of surrounding structural members.

tool from the rivet is minimized.

The improved method and means for detonating explosive type rivets contemplated by the present invention is further exemplified in Fig. 3 in which the shank I2 of the tool 0 is secured to the chuck 22 provided on one end of an angletype drilling attachment 23 having a drive shaft 24 on the other end thereof adapted to be rotatably driven either directly or through a flexible shaft by means of a motor such as illustrated at I8. The angle-type drilling attachment 23 is not in itself a part of this invention but is merely illustrative of a variety of small light tools commonly used and available for applying rotative power to fastenings and the like when located in confined or restricted areas, and where access to the head of the fastening is difficult or impossible to obtain with a relatively bulky motor or the like because of the configuration and prox- In the present case, the use ,of rotative power to detonate explosive-type rivets by means of the tool In permits the use of such attachments and therefore broadens the application of rivets of this type. The use of an angle-drilling attachment as exemplified at 23 in Fig. 3 permits use of the contemplated invention in areas congested by surrounding structure as generally shown, wherein it is impractical if not impossible to utilize the relatively heavy and cumbersome electrically heated irons conventionally employed.

As thus described, the present invention exemplifies an improved method of detonating explosive-type rivets comprising elevating the temperature of the rivet by frictional means to increase the speed of riveting, reduce cost, and improve results. The present invention may be accomplished by means comprising a rotatable tool having a head portion adapted to be held against the head of the rivet to elevate its temperature by friction, and being particularly adapted for minimum maintenance cost, and to facilitate riveting of the type under consideration in structures where access to the head of the rivet is dificult because of the proximity of the surrounding structural elements.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is: I

1. In the use of explosion type rivets having an internal charge adapted to be' detonated by elevating the temperature of the rivet, that im- Zprovement which consists in the steps of inserting the shank of said rivet into parts to be riveted, providing a surface that is relatively movable with respect to said rivet when so inserted,

and pressing said relatively moving surface against a portion of the external surface of the rivet for a suflicient length of time to detonate the said charge through temperature-elevation of said rivet responsive to friction created between the relatively moving surfaces.

2. The process of forming a riveted joint, comprising inserting the shank of an explosive rivet into parts to be riveted, providing a rotatable surface, and pressing said rotatable surface 20 against the head of the inserted rivet and causing rotation of said surface until said frictional 6 heat is developed as to explode the rivet and secure the parts in assembled relationship.

SALVATORE T. SPECIAL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I ENTS 

